The problem with just about every virtual desktop implementation is just that - they're virtual. This means that beyond the ability to move windows to specific desktops, you're still looking at exactly the same desktop, no matter what virtual desktop number you switched to. A mockup for GNOME Shell is trying to take the virtual out of virtual desktop.

Are they so difficult? The way desktops work where like I assumed they work when I first was introduced to virtual desktops in 1998/1999 on KDE 1 (I think it was KDE 1). It caused me some confusion until I've understood how they really work(ed).

The idea of virtual desktops isn't difficult, but can be hard for some people to visualise. They might be drawn side-by-side in a pager,but when you switch desktops, everything just vanishes, replaced by something else - there's no sense that you're moving somewhere.

Providing a visual transition makes them a lot easier to grasp - things like the Compiz cube, or having one desktop slide of the edge of the monitor.